Table of Contents

Driver test: high-MTU loopback

Rationale

To support operation as a VLAN trunk device, drivers should be able to support a frame size of 1518 bytes (excluding the Ethernet CRC), which corresponds to an MTU of 1504 bytes. The lotest command allows an arbitrary MTU to be specified, and so can easily be used to test operation with an MTU of 1504.

Background

Refer to the basic loopback test for background information.

A network card

Test sequence

  1. Before starting, ensure that your network interface is directly connected to a second network interface on the same machine.
  2. Boot into a version of iPXE with LOTEST_CMD enabled and with support for both network interfaces.
  3. Use ifstat to identify the name of your network interface (hereafter assumed to be net0) and the name of the second network interface (hereafter assumed to be net1).
  4. Initiate testing of the transmit datapath with an increased MTU using lotest --mtu 1504 net0 net1.
  5. Verify that the packet counter displayed by lotest increases steadily and rapidly.
  6. Abort the test using Ctrl-C.
  7. Initiate testing of the receive datapath with an increased MTU using lotest --mtu 1504 net1 net0.
  8. Verify that the packet counter displayed by lotest increases steadily and rapidly.
  9. Abort the test using Ctrl-C.
dev/drvtest/mtuloopback.txt ยท Last modified: 2013/04/03 15:22 by mcb30
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